Dated 1834-1837. From Scientific apparatus, musical instruments and telegraph equipment, [1834-1875].

Model developed by Peter Mark Roget (1779-1869), physician and philologist, to demonstrate the attractive force of parallel electrically charged wires. Consists of an extendable brass arm and spring or coil dipping into a mercury trough mounted on a wooden base. Possibly used by Wheatstone for teaching.  [See K/PP107/5/103.]